header is changed
previously, data packet and control message is differentiated
by the first byte. But it can be collide in some cases.
Now the first byte is version and the second byte is message type.
switchmode
Merge remote-tracking branch 'upstream/master' into header

Conflicts:
	src/gvpn_controller.py
	src/ipoplib.py
ipop switchmode
switchmode
removed unnecessary file
functions converting string to binary is changed

 - make_arp / send_packet separated
 - bugfix "local" field in arp_table
Merge pull request #4 from kyuhojeong/header

ARP handle